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Old 04-16-2011, 05:11 PM   #51 (permalink)
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Originally Posted by NeilBlanchard View Post
Hmmm.

Seems to me that almost 75% of petroleum energy used for transportation is wasted; compared to ~68.4% wasted in electricity.
I do not see where you got %68 at all for electric transportation. (or %75?)

petrol dominates transport, so lets say the product to waste ratio is: 6.74/20.23 or %33.3 efficient at doing work. That is business as usual, averaging the good and the bad. There isn't enough electric signal there to make any speculation about 68.4%

So we have two conversions to consider for electricity. First conversion is the 12.08/26.1, or %40 efficient, without having done any work.

If the stationary homes/industry/commercial are doing mostly things like heating, then the fuel use is going to be very efficient. Those three all rate 80% efficient, regardless of the mix of electric/fossile (possible red flag?) so it isn't a good basis for comparing to transportation (and we want to compare to petrol in transportation because we have petrol pretty well isolated in transportation, and this is a car site).

So we know that electricity from the wall can charge a car, the question is how efficient is that once you do some work.

Well, I think that saying electric cars are %70 efficient is terribly generous, especially "on average", even more so if it includes charging. Remember the goal isn't heat here, it is much more complicated. Regen is a separate issue.

So the two conversions multiplied to gether, %40 x %70, = %28 efficiency for electricity in vehicles. Compared to %33 for petrol transportation. Even if the transportation conversion step was %80 efficient for electricity, that would only be %32 efficient, still less than petrol overall (not counting wars and yadda).

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Old 04-16-2011, 10:23 PM   #52 (permalink)
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Look at the net numbers vs the total inputs.

For electricity 12.08 net vs 38.19 total input.

Transportation nets 6.74 net vs 26.98 total input.

Electricity and transportation are the two largest wasters, by far. By percentages, transportation is the worst: 6.74 / 20.23 = 0.333168561542264
Electricity is 12.08 / 26.10 = 0.462835249042146
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Old 04-17-2011, 12:09 PM   #53 (permalink)
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But remember that electric cars aren't the only user of electricity for transportation. (Indeed, they're probably a really minor user at present.) There's a good bit of electric mass transit: NYC subways, BART, some commuter rail in the northeast, and more.
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Old 04-17-2011, 12:57 PM   #54 (permalink)
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Vehicles that don't need batteries like electric trains are likely to be more efficient (or at least have more potential efficiency). But electric cars need batteries, for now anyway.
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Old 04-17-2011, 09:05 PM   #55 (permalink)
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This is sobering:

Technology Review "Just How Green Is Natural Gas?"

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Not green at all, reports a study suggesting that the methane released by fracking and drilling makes it worse than coal.
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Old 04-17-2011, 09:25 PM   #56 (permalink)
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I don't usually put much stock in those reports, at least without finding out the background of the people who ordered it. It's a very volatile subject, and a large number of groups stand to lose or gain from either end.

Being somewhat involved in the gas field, I see things that most don't, and as such, when some farmer comes to me talking about how his water is now flammable, I just hang my head and walk away...

Likewise, when the media reports about frac crews (there is no "k" in frac) and their "environmental impact", then show pics of a drill rig, or the coil tube rig, I can only think that someone should have done a bit more fact checking.

I don't necessarily agree with frac'ing, oil drilling, etc, but right now, it's provided a good many high wage jobs with benefits to an area that needed it, so people could care for their families who otherwise couldn't without financial aid.
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Old 04-18-2011, 01:26 AM   #57 (permalink)
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Quote:
Originally Posted by dcb View Post
I do not see where you got %68 at all for electric transportation. (or %75?)

petrol dominates transport, so lets say the product to waste ratio is: 6.74/20.23 or %33.3 efficient at doing work. That is business as usual, averaging the good and the bad. There isn't enough electric signal there to make any speculation about 68.4%

So we have two conversions to consider for electricity. First conversion is the 12.08/26.1, or %40 efficient, without having done any work.

If the stationary homes/industry/commercial are doing mostly things like heating, then the fuel use is going to be very efficient. Those three all rate 80% efficient, regardless of the mix of electric/fossile (possible red flag?) so it isn't a good basis for comparing to transportation (and we want to compare to petrol in transportation because we have petrol pretty well isolated in transportation, and this is a car site).

So we know that electricity from the wall can charge a car, the question is how efficient is that once you do some work.

Well, I think that saying electric cars are %70 efficient is terribly generous, especially "on average", even more so if it includes charging. Remember the goal isn't heat here, it is much more complicated. Regen is a separate issue.

So the two conversions multiplied to gether, %40 x %70, = %28 efficiency for electricity in vehicles. Compared to %33 for petrol transportation. Even if the transportation conversion step was %80 efficient for electricity, that would only be %32 efficient, still less than petrol overall (not counting wars and yadda).
I think we need to differentiate between the efficiency of oil used on personal transportation in a compact car versus the efficiency of oil used in transportation in general, and even the efficacy of oil used in transportation. For instance the efficiency of an SUV at 80mph on the highway is going to be fairly high even if it has poor efficacy. The flow-chart also doesn't show the energy inputs to industry that end up being used to refine oil, it just stops at industry. Supposedly road load plus charging is ~75% efficient for something like the AC-150, so a large manufacturer may actually do better, but in any event I think 70% for EVs is pretty reasonable.
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Old 04-18-2011, 12:42 PM   #58 (permalink)
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Quote:
Originally Posted by roflwaffle View Post
For instance the efficiency of an SUV at 80mph on the highway is going to be fairly high even if it has poor efficacy.
How so? Seems to me that in its default (i.e. most commonly seen) one person mode, it's pretty inefficient, even apart from the IC engine. You're accelerating a large mass, shoving lots of air out of the way, incurring rolling resistance from big tires...

Quote:
...in any event I think 70% for EVs is pretty reasonable.
There's also the second-order factors. So for oil you have 100% of a barrel in the ground somewhere in say Saudi Arabia. You need some amount of energy to pump it out of the ground & push it through pipelines to a loading dock, energy to run the oil tanker to destination, energy to run the refinery, more to run pipelines & delivery trucks, and a last little bit to run the pump at the gas station.

I don't know what that all adds up to, but it doesn't seem unreasonable that it'd be in the same range as a 30% grid plus charging loss for electric.
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Old 04-18-2011, 04:50 PM   #59 (permalink)
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Technically speaking that's efficacy. In the strictly thermodynamic sense a fully loaded tractor trailer will be more efficient than a prius, which is all the LLNL picture looks at, but realistically a prius will use way less gas no matter what, which is why we need to compare similar things instead of lumping everything together to get a valid conclusion given the subject matter (EV car versus ICE car).
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Old 04-18-2011, 05:38 PM   #60 (permalink)
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Quote:
Originally Posted by roflwaffle View Post
In the strictly thermodynamic sense a fully loaded tractor trailer will be more efficient than a prius...
Still a bit puzzled, but I'm not sure the highway-cruising SUV doesn't lose out there, too. That is, it's got a big engine (for acceleration, towing those 10,000 lb boats & camping trailers, etc), which in highway cruising would likely be running far from its optimum BSFC, so inefficient. Whereas diesel semi (as you know if you've ever followed on up a long grade) has engine HP more closely matched to cruising load.

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